In 1976, Barry Kidston, a chemistry grad student, would find out the hard way that you had better be careful with your reaction conditions when making psychoactive drugs. He got a little sloppy, and instead of making a pure derivative of Demerol, got an impurity in the batch, which gave him Parkinson's with one injection. Six years later, a group of six "frozen addicts" suffered the same fate. Crazy brain chemistry.